Various types of lift gates are commercially available for installation and use in motor vehicles. A common characteristic of a lift gate is that it comprises a platform that can be raised and lowered to allow a load to be loaded onto or unloaded from a vehicle and thereafter stowed.
For example, a typical lift gate may be installed at the rear of the bed or cargo area of a truck. The lift gate can be lowered to ground level to allow a load to be placed on the lift gate platform. The platform is then raised to the level of the truck bed or cargo floor where the load can be moved onto the bed or floor. When the load is to be unloaded, it is placed on the platform, and the lift gate is lowered to ground level where the load can be moved off the platform. When not being used, the lift gate is typically operated to a stowed position where the platform is either generally vertical or folded in under the bed.
It is typical for the vehicle's own electrical power to be used for powering the lift gate. One type of lift gate has an electric motor that raises and lowers the platform through a mechanical mechanism. Another type has an electric motor that operates a hydraulic pump that provides hydraulic power for operating the lift gate. Operation may occur through one or more hydraulic cylinders.
In all of those cases, electric power for raising and lowering the lift gate is drawn from the motor vehicle's electrical system although it is to be appreciated that more power is likely to be drawn when a load on the lift gate platform is being raised than when it is being lowered.
When the engine that powers the motor vehicle is running, an alternator supplies the vehicle electrical system needs while keeping the vehicle battery or battery bank charged to proper voltage. When the engine is not running, the vehicle electrical system needs must be supplied by the vehicle battery or battery bank. Because operation of a vehicle's lift gate will usually occur while the vehicle is parked, the lift gate has to draw electricity solely from the battery or battery bank if the engine is not kept idling while the vehicle is parked.
If a lift gate is powered directly from a battery or battery bank through a circuit breaker, battery power remains available to the lift gate thereby raising the possibility for unauthorized operation of the lift gate. Moreover, the batteries can possibly be discharged to the point where they cannot operate the lift gate any more, and consequently will be incapable of starting the engine.